People living near the volcano in Central Java province said the explosion at around 1:00 am was louder and stronger than the eruptions that killed 34 people on Tuesday.

Soldiers and police posted nearest the volcano were seen fleeing along with hundreds of ordinary people, who quickly clogged roads with cars and motorcycles as black soot fell across a vast area.

“My neighbours told me to leave and my village is already empty — everyone has fled,” said 42-year-old resident Mukinem, who was heading away from the volcano on a motorcycle with her husband and two young children.

“I heard several sounds like thunder. I was so scared I was shaking.”

A resident of Hargobinangun just outside the 10-kilometer exclusion zone established by the government said the eruption was “more than twice as big as the first eruption on Tuesday.”

Government volcanologists were not immediately available to confirm the strength of the new activity.

At least two people were taken to hospital with burn injuries, witnesses said.

The 2,914-metre Mount Merapi, which means “Mountain of Fire”, is the most active of the 69 volcanoes with histories of eruptions in Indonesia.

More than 50,000 people are living in cramped temporary shelters near the central Java city of Yogyakarta after being ordered to evacuate on Monday.

But officials have said many have returned to feed their livestock or check their properties, and it is not known how many people were on the mountain during the latest eruption.